1. Field of the Invention
The present invention relates to a hydraulic system for a detachable implement having multiple hydraulic motors and in particular to a hydraulic system for a harvester header, such as a draper platform.
2. Description of Related Art
Draper platforms for harvesting machines, such as a combine, have a flat, wide belt, referred to as a draper or draper belt, to convey crop material. The arrangement and number of draper belts vary among platforms. One style of draper platform has two side belts that convey crop material laterally, to the center of the platform, where a center feed draper belt moves the crop material longitudinally into a combine feederhouse. Each of the draper belts is driven by a hydraulic drive motor.
In addition to the draper belts, a draper platform uses another hydraulic motor to rotate a reel above a cutterbar to hold crop material against the cutterbar and to move the cut crop material onto the draper belts. Hydraulic lift cylinders are used to raise and lower the reel as well as to position the reel fore and aft relative to the cutterbar.
A conventional combine includes a hydraulic system with connections for driving the platform reel and connections for operating the reel lift cylinders and the reel fore and aft adjustment cylinders. In addition to the hydraulic connections to the platform, the combine includes a power take off (PTO) for a mechanical power connection. The PTO is typically used to mechanically drive the platform cutterbar and crop conveying augers if the platform is so equipped.
Combines typically do not have additional hydraulic power connections for operating the draper belt drive motors. Therefore other provisions must be made for providing hydraulic power for this purpose. One option is to provide a complete hydraulic system on the platform including a gear pump that is driven by the combine PTO. This approach requires that the platform hydraulic system be equipped with a reservoir, filter and cooling package. This adds significant cost, weight and complexity to the draper platform. In addition, the PTO shaft speed is typically lower than required for efficient operation of a gear pump.
A second option is to provide additional pump capacity on the combine, thereby utilizing existing combine hydraulics to power the draper belt drive motors. A major disadvantage with this approach is the need for significant combine modifications in retrofit applications, as well as the need for another set of hydraulic hoses and couplers between a combine and the platform.